first = float(input("请输入第一个数:"))
second = float(input("请输入第二个数:"))
operator = input("请选择运算符: + - * /:")
if operator == '+':
    print(first + second)
elif operator == '-':
    print(first - second)
elif operator == '*':
    print(first*second)
elif operator == '/':
    if second == 0:
     print("除数不能为0")
else:
    print(first / second)